Apparatus for making extracorporeal blood circulation available

ABSTRACT

The present invention relates to an apparatus for making extracorporeal blood circulation available, in particular a heart-lung machine, comprising a venous connection and an arterial connection, between which a blood reservoir, a blood pump and a bubble detector for the detection of air bubbles are provided, with, downstream of the bubble detector, an arterial line leading to the arterial connection via an arterial clamp and a bypass leading via a bypass clamp back into the blood reservoir which is connected to a pump extracting air from the blood reservoir. In addition, the present invention relates to a method of operating such an apparatus.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/064,988 filed Oct. 28, 2013 and issuing as U.S. Pat. No. 8,951,220 onFeb. 10, 2015, which us a continuation of U.S. patent application Ser.No. 13/466,899 filed May 8, 2012 and issued as U.S. Pat. No. 8,568,347on Oct. 29, 2013, which is a division of U.S. patent application Ser.No. 11/554,524 filed Oct. 30, 2006 and issued as U.S. Pat. No. 8,187,214on May 29, 2012, the entire disclosure of each such patent and patentapplication being expressly incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an apparatus for making extracorporealblood circulation available, in particular a so-called heart-lungmachine. Apparatus of this type can replace the pump function of theheart and the lung function for a limited period of time. The blood ofthe patent is introduced via a venous connection into the extracorporealblood circuit and is pumped by a blood pump via differentblood-conducting components to an arterial connection from where theblood is again pumped into the patient's blood circulation.

BACKGROUND

When such an extracorporeal blood circuit is used, air bubbles may forminside the blood circuit. In addition, air which was included in theblood circuit on the putting into operation of the extracorporeal bloodcircuit can enter into the blood. An air bubble which enters into thepatient's blood circulation can cause a fatal air embolism in the worstcase.

This problem has been known for some time and there are differentstrategies to avoid air bubbles being located in the blood exiting theextracorporeal blood circuit via the arterial connection. There are, forexample, air bubble detectors which can detect air bubbles in the bloodstream. With the previously known systems, a visual or acoustic alarmsignal is output on detection of an air bubble and the blood supply tothe patient is stopped. Subsequently, the medical personnel on hand mustact as fast as possible since the problem has to be eliminated and thepatent has to be treated further. Equally, different components areknown which should filter air bubbles out of the blood, for exampleblood filters which collect and retain both particles and gas bubbles.

SUMMARY

It is the object of the present invention to further reduce the risk ofthe occurrence of air embolisms in the operation of apparatus of theinitially named kind. In this connection, human intervention should notbe necessary if at all possible.

This object is satisfied by the apparatus in accordance with theindependent apparatus claims and by the corresponding methods inaccordance with the independent method claims.

In accordance with the invention, a blood reservoir, a blood pump whichreplaces the pump function of the heart, and a bubble detector for thedetection of air bubbles are provided between the venous connection andthe arterial connection. The blood entering at the venous connection ispumped by the blood pump through the blood reservoir and, optionally,through further blood-conducting components via the bubble detector upto the arterial connection. Downstream of the bubble detector, anarterial line which can be closed by an arterial clamp leads to thearterial connection via which the blood is again conducted into thepatient's blood circulation. If the bubble detector detects an airbubble, the arterial clamp can be closed immediately so that the airbubble cannot enter into the patient's blood circulation. At the sametime, a bypass clamp is opened so that the blood is guided back into theblood reservoir through a bypass. The blood reservoir is connected to afurther pump which can actively extract air from the blood reservoir.The air bubbles rising upwardly in the blood reservoir are extracted bythis pump and, as soon as the bubble detector no longer detects any airbubbles, the arterial clamp is opened again and the bypass clamp isclosed again.

It is ensured by a sufficiently long reaction path between the bubbledetector and the arterial clamp and by a short reaction tie of thearterial clamp, which is preferably a fast-closing clamp such as isdescribed in U.S. patent application Ser. No. 11/366,914 (now U.S. Pat.No. 7,367,540) that the detected air bubble cannot flow through thearterial clamp to the arterial connection before said arterial clampclosed.

The apparatus in accordance with the invention therefore reactsautomatically to the detection of an air bubble and eliminates it. Assoon as the air bubble has been eliminated, the patient is againsupplied with blood as before without any human intervention having beennecessary. This in particular increases safety with a portable devicefor the provision of an extracorporeal blood circuit such as isdescribed in U.S. patent application Ser. Nos. 11/284,515 and 10/839,126(now U.S. Pat. Nos. 7,846,122 and 7,682,327 respectively), whosedisclosure is made part of this application by reference. The emergencyphysician must only connect the patient properly to the apparatus inaccordance with the invention and can then dedicate himself to thefurther medical care of the patient, while the apparatus eliminates therisk of an air embolism with high probability without humanintervention.

Advantageous embodiments of the present invention are described in thedependent claims and in the now following description.

In accordance with an advantageous embodiment of the invention, anoxygenator which enriches the blood with oxygen and thus takes over thefunction of the lung is arranged between the blood pump and the bubbledetector. The oxygenator likewise contributes to the elimination of anyair bubbles present since these are held back at the membrane present inthe oxygenators used today. An arterial filter which collects and holdsback microparticles which have entered into the blood as well as gasbubbles can furthermore be provided in front of the bubble detector.

It is particularly advantageous for blood-conducting components of theapparatus such as an oxygenator or an arterial filter to be connected tothe blood reservoir via a venting line. The venting line can in thisconnection be closed by venting clamps and primarily serves for flushingand venting during a priming process before the actual putting intooperation of the apparatus. The venting clamps can, however, also beopened briefly during the operation of the apparatus at regular timeintervals so that air which has collected in the blood-conductingcomponents is introduced into the reservoir. The air then rises to thesurface in the reservoir and can be extracted by the pump provided forthis purpose. The venting line is connected to the blood-conductingcomponents in each case at their side disposed upwardly in operation sothat upwardly rising air bubbles migrate into the venting line. Asaturation of the blood-conducting components with air is avoided bythis regular venting and the risk of an air bubble moving up to thebubble detector at all is reduced.

In accordance with a further advantageous embodiment of the invention,the blood pump is made as a centrifugal pump. Since centrifugal pumpscannot transport any real air volumes, the probability that the bloodexiting the apparatus contains air bubbles is further reduced simply bythe use of a centrifugal pump. In addition, the centrifugal pump can beprovided with a central inlet and a tangential outlet, with thetangential outlet advantageously being arranged such that it facesdownwardly when the apparatus is in an operation position. Since any airbubbles present in the pump head rise upwardly, the probability of thetransport of air bubbles is further reduced by this geometry.

The pump extracting the air from the blood reservoir is preferably aroller pump which can additionally have a clamping function. Such a pumpis described in U.S. patent application Ser. No. 11/366,342 and permitsthe extraction of air from the blood reservoir with simple means, withit being ensured by the clamping function that no air can flow in theopposite direction, i.e. into the reservoir, even when the pump isswitched off.

In accordance with an advantageous embodiment of the invention, an aircontainer is arranged downstream of this pump extracting air from theblood reservoir and the air extracted from the reservoir is pumped intoit. The total extracorporeal blood circuit thereby remains closed towardthe outside. A simple plastic pouch can serve as the air container.

Additional protection from air bubbles in the blood exiting theapparatus can be achieved in that the blood reservoir is split up intoan inlet region and an outlet region by a membrane permeable for blood,but impermeable for air bubbles.

In accordance with a further advantageous embodiment of the invention,means are provided for the monitoring of the filling level of the bloodreservoir. A first sensor is preferably provided which detects whetherthe filling level reaches a first threshold value. A second sensordetects whether the filling level falls below a second threshold valuelying below the first threshold value. The corresponding information canbe passed on to an electronic control unit of the apparatus so that, ona falling below of the first threshold value, the pump can be switchedon to extract air from the blood reservoir. The air which collects inthe blood reservoir in bypass operation after detection of an air bubbleor on a regular venting of blood-conducting components is thus extractedautomatically as soon as a certain air amount is present in thereservoir. As further security, the blood pump can be switched off ifthe filling level falls below the second threshold value. In this case,an alarm signal is simultaneously output. It is possible for the fillinglevel of the reservoir to fall below the second threshold value, forexample, if the venous connection is not properly connected to thepatient's blood circulation, but has become loose so that only air issucked through. In such cases, the blood pump is switched offimmediately thanks to the described filling level monitoring.

In accordance with a further advantageous embodiment of the invention,the bypass clamp is opened at regular time intervals for a short periodto flush the bypass. It is thereby avoided that blood standing in thebypass in front of the closed bypass clamp coagulates and that thiscoagulated blood then enters into the extracorporeal blood circuit afterthe opening of the bypass clamp and, in the worst case, subsequently viathe arterial connection into the patient's blood circulation.

The probability that an air bubble enters into the patient's bloodcirculation and triggers an air embolism is considerably lowered by theinteraction of the described features. An intervention of the trainedmedical staff due to an error report is only necessary in an extremeemergency. In the normal case, the apparatus in accordance with theinvention can successfully prevent air bubbles entering into the bloodcirculation of the patient connected to the apparatus without any humanintervention.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention should be described in more detail in the following withreference to a preferred embodiment and to the enclosed FIGURE.

The enclosed FIG. 1 shows a schematic representation of the individualcomponents of a heart-dung machine.

DETAILED DESCRIPTION

The following description of the preferred embodiment is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

The patient blood coming from a venous connection V is guided via a line18 into a blood reservoir 20 and moves from there via an outlet 23 intoan inlet 34 of a centrifugal pump 30. The inlet 34 is arranged centrallyat a pump head of the centrifugal pump 30. The blood is pumped via atangential outlet 32 arranged at the bottommost point of the pump headof the centrifugal pump 30 into an oxygenator 40 to which an oxygensupply line is connected. The blood enriched with oxygen is subsequentlyfiltered in an arterial filter 44 and finally flows, in the normal case,through an arterial line 68 via the arterial connection A back into thebody of the patient.

The blood reservoir 20 is split into an inlet region (at the top inFIG. 1) and an outlet region (at the bottom in FIG. 1) by a membrane 28.The membrane 28 is permeable for blood, but prevents air bubblesentering into the outlet region from the inlet region.

A bubble detector 50 is arranged between the arterial filter 44 and thearterial connection A. As long as it does not detect any air bubbles, anarterial clamp 60 in the arterial line 68 remains open, while a bypassclamp 62 remains closed. A throughflow sensor 66 measures the blood flowin the arterial line 68 so that said blood flow can be constantlymonitored.

If an air bubble is detected in the bubble detector 50, the arterialclamp 60 is closed immediately. The reaction path between the bubbledetector 50 and the arterial clamp is so long that the detected airbubble only reaches the clamp when this has already been closed. Theclamp 60 is a fast-closing clamp which closes in less than 300 ms. Sucha fast-closing clamp is described in U.S. patent application Ser. No.11/366,914 to which reference is herewith made. It can be precluded bythe sufficiently long reaction path and the fast closing of the clampthat the air bubble detected in the bubble detector 50 can reach up tothe arterial connection A before the closing of the clamp 60.

At the same time, the bypass line 62 is opened so that the blood,together with the detected air bubble, flows via a bypass 64 back intothe line 18 and into the blood reservoir 20.

In the blood reservoir 20, air bubbles rise upwardly so that the bloodis located at the bottom in the reservoir, while air collects at thetop. Means 22 for the monitoring of the filling level of the bloodreservoir are electronically coupled to a roller pump 70 for theextraction of air from the reservoir, for example via an electroniccontrol unit. As soon as the means 22 for the monitoring of the fillinglevel of the blood reservoir 20 report that the filling level has fallenbelow a first threshold value, the roller pump 70 is switched on,extracts the air present at the top in the reservoir 20 and pumps itinto an air container 80. The roller pump 70 has a clamping function sothat it acts as a clamp if it is not actively pumping and prevents abackflow of air into the blood reservoir 20.

If the filling level of the blood reservoir falls further despite thepumping away of air by the roller pump 70 and if it falls below a secondthreshold value, for example because the venous connection V is notproperly connected, the centrifugal pump 30 is switched off and an alarmsignal is output.

The oxygenator 40 and the arterial filter are each connected to theupper region of the blood reservoir 20 not filled with blood via aventing line 96 provided with venting valves 92, 94. The venting linefirst serves for the flushing and venting of the heart-lung machineduring a priming procedure before its putting into operation. In thisconnection, a so-called priming liquid is filled in via a primingconnection PR and the extracorporeal blood circuit is vented. Thepriming circuit is shown by broken lines in FIG. 1. The venting clamps92 and 94 are normally closed during the operation of the heart-lungmachine. They are, however, opened briefly at regular time intervals,for example every 10 to 15 minutes, so that air which has collected inthe oxygenator or the arterial filter is guided into the reservoir 20and can be extracted from there.

The reference numerals 24 and 26 designate pressure sensors whichmonitor the pressure before and after the oxygenator. The measuredvalues of the pressure sensors are forwarded to a pressure monitoringunit 27 via a connection not shown in FIG. 1 for reasons of clarity. Inthe event of an unusually increasing pressure drop at the oxygenator 40,this can be clogged by coagulated blood so that there is a need foraction.

In addition, the extraction pressure at which blood is extracted fromthe patient into the line 18 is monitored with the aid of a pressuresensor 25. In this connection, the line anyway present between the bloodreservoir 20 and the roller pump 70 is utilized to measure thispressure. The measured result is likewise passed on to the pressuremonitoring unit 27.

To avoid blood standing in the bypass 64 in FIG. 1 beneath the bypassclamp 62 coagulating while the arterial clamp 60 is open and the bypassclamp 62 is closed, the bypass clamp 62 is opened at regular timeintervals for a short period. The bypass 64 is periodically flushed inthis manner so that blood coagulation cannot occur in the bypass 64.

The description of the invention is merely exemplary in nature and,thus, variations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

What is claimed is:
 1. An apparatus for making extracorporeal blood circulation available to a subject, said apparatus comprising: a venous connection and an arterial connection, between which there are positioned; a venous flow path which carries blood from the venous connection into a blood reservoir configured to separate air from blood, said blood reservoir having a first sensor which senses when liquid in the reservoir reaches a first threshold level and second sensor which senses when liquid in the reservoir reaches a second threshold level, said blood reservoir being connected to an air extraction pump which extracts air from the blood reservoir, a blood pump, a filter, a bubble detector located downstream of the filter, an arterial flow path leading from the bubble detector to the arterial connection, a bypass flow path leading from a location on the arterial flow path downstream of both the filter and bubble detector to a location on the venous flow path upstream of the blood reservoir, a bypass clamp positioned on the bypass flow path, an arterial clamp positioned on the arterial flow path downstream of its connection to the bypass flow path and upstream of the arterial connection, and a bypass clamp on the bypass flow path; wherein the apparatus further comprises an electronic control unit which receives signals from the first and second sensors and is programmed to automatically a) cause the air extraction pump to remove air from the reservoir when signals received from the first sensor indicate that the liquid level in the reservoir is below the first threshold level, b) cause the blood pump to stop when signals received from the second sensor indicate that the liquid level in the reservoir has fallen below the second threshold level, and c) cause an alarm signal to be output when signals received from the second sensor indicate that the liquid level in the reservoir has fallen below the second threshold level; wherein the electronic control unit also receives signals from the bubble detector and is programmed to respond to detection of a bubble by the bubble detector during operation of the apparatus by closing the arterial clamp and opening the bypass clamp such that blood and the detected bubble will pass from the arterial flow path, though the bypass flow path and become combined with venous blood flowing from the venous connection through the venous flow path and into the reservoir.
 2. An apparatus in accordance with claim 1, wherein at least one of an oxygenator and an arterial filter is provided between the blood pump and the bubble detector.
 3. An apparatus in accordance with claim 1, wherein: air separates from blood within the blood reservoir and the separated air collects in an air collection region of the blood reservoir; and the pump which extracts air from the blood reservoir is automatically actuated, without human intervention, when a predetermined amount of air has collected in the air collection region of the blood reservoir.
 4. An apparatus in accordance with claim 1, wherein the blood pump is made as a centrifugal pump with a central inlet and a tangential outlet, with the tangential outlet facing downwardly when the apparatus is in an operating position.
 5. An apparatus in accordance with claim 1, wherein the air extraction pump comprises is a roller pump.
 6. An apparatus in accordance with claim 1, wherein an air container is arranged downstream of the pump extracting air from the blood reservoir.
 7. An apparatus in accordance with claim 1, wherein the blood reservoir is split into an inlet region and an outlet region by a membrane impermeable for air bubbles.
 8. An apparatus in accordance with claim 1, wherein means are provided for the monitoring of the filling level of the blood reservoir.
 9. An apparatus according to claim 1 wherein, upon detection of a bubble by the bubble detector, the bypass clamp opens and the arterial clamp closes, thereby causing blood and the detected bubble to circulate from said location downstream of the filter and bubble detector, through the bypass flow path, and back into the blood reservoir.
 10. An apparatus for making extracorporeal blood circulation available to a subject, said apparatus-comprising a venous connection and an arterial connection, between which there is a venous blood inflow conduit that extends from the venous connection to a blood reservoir that is split into an inlet region and an outlet region by a membrane through which air bubbles do not pass, said blood reservoir having sensing apparatus for the monitoring of the filling level of the blood reservoir and an air vent for venting air that collects in the inlet region of the reservoir, a centrifugal blood pump, an oxygenator, an arterial filter, a bubble detector positioned downstream of the arterial filter so as to detect any air bubbles that pass out of the arterial filter and an arterial line leading to the arterial connection via an arterial clamp and a bypass line leading via a bypass clamp from said arterial line downstream of both the arterial filter and the bubble detector positioned downstream of the arterial filter, back into the blood reservoir, said blood reservoir being connected to a roller pump which conveys air from the blood reservoir into an air container and a control unit; wherein detection of a bubble by the bubble detector results in closure of the arterial clamp and opening of the bypass clamp, thereby causing blood and the detected bubble to circulate through the bypass and into the venous inflow conduit where it becomes combined with venous blood flowing from the venous connection to the reservoir; wherein the control unit receives information from the sensing apparatus; and wherein, when information received from the sensing apparatus indicates that the filling level in the reservoir has fallen below an upper threshold level, the control apparatus automatically causes air to be vented from the blood reservoir and, when information received from the sensing apparatus indicates that the filling level in the reservoir has fallen below a lower threshold level, the control apparatus automatically causes the blood pump to stop and an alarm signal to be output.
 11. An apparatus according to claim 10 wherein the bypass clamp opens at intervals to flush standing blood from the bypass line.
 12. An apparatus according to claim 10 further comprising venting lines which connect the oxygenator and arterial filter to the reservoir.
 13. An apparatus according to claim 12 wherein the venting lines have venting line clamps which are opened at intervals to flush the venting lines.
 14. An apparatus for making extracorporeal blood circulation available to a subject, said apparatus comprising: an inflow connection connectable to the vasculature of a subject; an outflow connection connectable to the vasculature of the subject; a blood reservoir having a first sensor which senses when liquid in the reservoir reaches a first threshold level and second sensor which senses when liquid in the reservoir reaches a second threshold level; an air pump for extracting air from the blood reservoir; a blood pump; at least one blood processing component selected from a blood filter and a blood oxygenator; a first conduit through which blood may flow from the inflow connection to the blood reservoir; a second conduit, through which blood may flow from the blood reservoir to said at least one blood processing component; a third conduit through which blood may flow from said at least one blood processing component to the outflow connection; a filter for filtering blood flowing through the third conduit a bubble detector on the third conduit downstream of the filter; a clamp for stopping blood flow through the third conduit at a location downstream of the filter and bubble detector; a bypass conduit extending from a location on the third conduit downstream of the filter and bubble detector and upstream of the clamp, to a location on the first conduit between the inflow connection and the blood reservoir; electronic apparatus which causes the clamp to close in response to the detection of an air bubble by the bubble detector, wherein said closing of the clamp causes the flow of blood and the detected bubble to be diverted from said location on the third conduit, through the bypass conduit, and into the first conduit wherein it flows, along with venous blood entering through the inflow connection, into the Hood reservoir; and electronic apparatus which receives signals from the first and second sensors and is programmed to automatically a) cause the air pump to remove air from the reservoir when signals received from the first sensor indicate that the liquid level in the reservoir is below the first threshold level, b) cause the blood pump to stop when signals received from the second sensor indicate that the liquid level in the reservoir has fallen below the second threshold level, and c) cause an alarm signal to be output when signals received from the second sensor indicate that the liquid level in the reservoir has fallen below the second threshold level.
 15. An apparatus in accordance with claim 14 wherein said at least one blood processing component comprises a blood filter.
 16. An apparatus in accordance with claim 14 wherein said at least one blood processing component comprises a blood oxygenator.
 17. An apparatus in accordance with claim 14 wherein said at least one blood processing component comprises a blood oxygenator and a blood filter.
 18. An apparatus in accordance with claim 17 wherein the blood oxygenator and blood filter are in series such that blood flows through the blood oxygenator and thereafter flows through the blood titter.
 19. An apparatus in accordance with claim 14, wherein said at least one blood processing component is/are connected to the blood reservoir via one or more venting lines, with one or more venting line clamps for alternately opening and closing said one or more venting lines.
 20. An apparatus in accordance with claim 14, wherein the blood pump comprises a centrifugal pump having a central inlet and a tangential outlet, with the tangential outlet facing downwardly when the apparatus is in an operating position.
 21. An apparatus in accordance with claim 14 wherein the air pump comprises a roller pump.
 22. An apparatus in accordance with claim 14 further comprising an air container positioned downstream of the air pump to receive air that is extracted from the blood reservoir.
 23. An apparatus in accordance with claim 14 wherein the blood reservoir comprises an inlet region and an outlet region, the inlet and outlet regions being separated by a membrane through which air bubbles will not pass.
 24. An apparatus in accordance with claim 14 further comprising sensing apparatus for sensing the level of blood within the blood reservoir. 